Current progress on in vitro differentiation of ovarian follicles from pluripotent stem cells.

Mammalian female reproduction requires a functional ovary. Competence of the ovary is determined by the quality of its basic unit-ovarian follicles. A normal follicle consists of an oocyte enclosed within ovarian follicular cells. In humans and mice, the ovarian follicles are formed at the foetal and the early neonatal stage respectively, and their renewal at the adult stage is controversial. Extensive research emerges recently to produce ovarian follicles in-vitro from different species. Previous reports demonstrated the differentiation of mouse and human pluripotent stem cells into germline cells, termed primordial germ cell-like cells (PGCLCs). The germ cell-specific gene expressions and epigenetic features including global DNA demethylation and histone modifications of the pluripotent stem cells-derived PGCLCs were extensively characterized. The PGCLCs hold potential for forming ovarian follicles or organoids upon cocultured with ovarian somatic cells. Intriguingly, the oocytes isolated from the organoids could be fertilized in-vitro. Based on the knowledge of in-vivo derived pre-granulosa cells, the generation of these cells from pluripotent stem cells termed foetal ovarian somatic cell-like cells was also reported recently. Despite successful in-vitro folliculogenesis from pluripotent stem cells, the efficiency remains low, mainly due to the lack of information on the interaction between PGCLCs and pre-granulosa cells. The establishment of in-vitro pluripotent stem cell-based models paves the way for understanding the critical signalling pathways and molecules during folliculogenesis. This article aims to review the developmental events during in-vivo follicular development and discuss the current progress of generation of PGCLCs, pre-granulosa and theca cells in-vitro.

Attachment of a trophoblastic spheroid onto endometrial epithelial cells predicts cumulative live birth in women aged 35 and older.

OBJECTIVE: To evaluate the attachment rate of a human embryonic stem cell-derived trophoblastic spheroid onto endometrial epithelial cells in predicting the cumulative live birth rate of an in vitro fertilization (IVF) cycle. DESIGN: A prospective observational study. SETTING: University hospital and research laboratory. PATIENT(S): A total of 240 infertile women from 2017-2021. INTERVENTION(S): Infertile women with regular cycles attending for IVF were recruited. An endometrial aspirate was collected from a natural cycle 1 month before IVF to determine the BAP-EB attachment rate. MAIN OUTCOME MEASURE(S): Cumulative live birth rates from a stimulated cycle and its derived frozen embryo transfer cycles within 6 months of ovarian stimulation were obtained. RESULT(S): The BAP-EB attachment rate in women who attained a cumulative live birth was similar to that in those who did not. When women were stratified by age into <35 years and ≥35 years, the BAP-EB attachment rate was significantly higher only in women aged ≥35 years having a live birth when compared with those in the same age group without a live birth. Receiver operating characteristic curve analysis of BAP-EB attachment rate in predicting cumulative live birth showed the areas under the curve of 0.559 (95% confidence interval [CI], 0.479-0.639), 0.448 (95% CI, 0.310-0.585), and 0.613 (95% CI, 0.517-0.710) for all ages, an age of <35 years, and an age of ≥35 years, respectively. CONCLUSION(S): The BAP-EB attachment rate offers only a very modest prediction of the cumulative live birth rate in women aged ≥35 years undergoing IVF. CLINICAL TRIAL REGISTRATION NUMBER: NCT02713854 (https://clinicaltrials.gov/ct2/show/NCT02713854; Date of registration, March 21, 2016; date of enrollment of the first subject, August 1, 2017).

Non-Coding RNAs as Biomarkers for Embryo Quality and Pregnancy Outcomes: A Systematic Review and Meta-Analysis.

Despite advances in in vitro fertilization (IVF), there is still a lack of non-invasive and reliable biomarkers for selecting embryos with the highest developmental and implantation potential. Recently, small non-coding RNAs (sncRNAs) have been identified in biological fluids, and extracellular sncRNAs are explored as diagnostic biomarkers in the prediction of IVF outcomes. To determine the predictive role of sncRNAs in embryo quality and IVF outcomes, a systematic review and meta-analysis was performed. Articles were retrieved from PubMed, EMBASE, and Web of Science from 1990 to 31 July 2022. Eighteen studies that met the selection criteria were analyzed. In total, 22 and 47 different sncRNAs were found to be dysregulated in follicular fluid (FF) and embryo spent culture medium (SCM), respectively. MiR-663b, miR-454 and miR-320a in FF and miR-20a in SCM showed consistent dysregulation in two different studies. The meta-analysis indicated the potential predictive performance of sncRNAs as non-invasive biomarkers, with a pooled area under curve (AUC) value of 0.81 (95% CI 0.78, 0.844), a sensitivity of 0.79 (95% CI 0.72, 0.85), a specificity of 0.67 (95% CI 0.52, 0.79) and a diagnostic odds ratio (DOR) of 8 (95% CI 5, 12). Significant heterogeneity was identified among studies in sensitivity (I2 = 46.11%) and specificity (I2 = 89.73%). This study demonstrates that sncRNAs may distinguish embryos with higher developmental and implantation potentials. They can be promising non-invasive biomarkers for embryo selection in ART. However, the significant heterogeneity among studies highlights the demand for prospective multicenter studies with optimized methods and adequate sample sizes in the future.

Expanded Potential Stem Cells from Human Embryos Have an Open Chromatin Configuration with Enhanced Trophoblast Differentiation Ability.

Human expanded potential stem cells (hEPSC) have been derived from human embryonic stem cells and induced pluripotent stem cells. Here direct derivation of hEPSC from human pre-implantation embryos is reported. Like the reported hEPSC, the embryo-derived hEPSC (hEPSC-em) exhibit a transcriptome similar to morula, comparable differentiation potency, and high genome editing efficiency. Interestingly, the hEPSC-em show a unique H3 lysine-4 trimethylation (H3K4me3) open chromatin conformation; they possess a higher proportion of H3K4me3 bound broad domain (>5 kb) than the reported hEPSC, naive, and primed embryonic stem cells. The open conformation is associated with enhanced trophoblast differentiation potency with increased trophoblast gene expression upon induction of differentiation and success in derivation of trophoblast stem cells with bona fide characteristics. Hippo signaling is specifically enriched in the H3K4me3 broad domains of the hEPSC-. Knockout of the Hippo signaling gene, YAP1 abolishes the ability of the embryo-derived EPSC to form trophoblast stem cells.

Endometrial stromal cells from women with repeated implantation failure display impaired invasion towards trophoblastic spheroids.

In brief: Implantation failure can occur even after the transfer of good-quality embryos. This study showed that the migration of human endometrial stromal cells towards embryonic trophoblasts is higher in women with live births in the first in vitro fertilization cycle than those with repeated implantation failure, suggesting that the chemotactic response of stroma cells is associated with successful pregnancy. Abstract: The success rate of in vitro fertilization (IVF) remains limited in some women despite transfers of good-quality embryos in repeated attempts. There is no reliable tool for assessing endometrial receptivity. This study aimed to assess the interaction between decidualized human primary endometrial stromal cells (1°-EnSC) and human embryonic stem cell-derived trophoblastic spheroids (BAP-EB) and to compare the invasion ability of decidualized 1°-EnSC towards BAP-EB between women attaining live birth in the first IVF cycle and those with repeated implantation failure (RIF). The invasion of the decidualized human endometrial cell line (T-HESC) and 1°-EnSC towards BAP-EB was studied. Real-time quantitative PCR and immunocytochemistry were employed to determine the expression of decidualization markers at mRNA and protein levels, respectively. Trophoblast-like BAP-EB-96h, instead of early trophectoderm (TE)-like BAP-EB-48h, facilitated the invasion ability of decidualized T-HESC and decidualized 1°-EnSC. Human chorionic gonadotropin at supra-physiological levels promoted the invasiveness of decidualized 1°-EnSC. The extent of BAP-EB-96h-induced invasion was significantly stronger in decidualized 1°-EnSC from women who had a live birth in the first IVF cycle when compared to those with RIF. While no difference was found in the expression of decidualization markers, PRL and IGFBP1 among two groups of women, significantly lower HLA-B was detected in the non-decidualized and decidualized 1°-EnSC from women with RIF. Collectively, the findings suggested that the invasion of decidualized 1°-EnSC towards trophoblast-like BAP-EB-96h was higher in women who had a live birth in the first IVF cycle than those with RIF.

Hyperglycemia Altered DNA Methylation Status and Impaired Pancreatic Differentiation from Embryonic Stem Cells.

The prevalence of type 2 diabetes (T2D) is rapidly increasing across the globe. Fetal exposure to maternal diabetes was correlated with higher prevalence of impaired glucose tolerance and T2D later in life. Previous studies showed aberrant DNA methylation patterns in pancreas of T2D patients. However, the underlying mechanisms remained largely unknown. We utilized human embryonic stem cells (hESC) as the in vitro model for studying the effects of hyperglycemia on DNA methylome and early pancreatic differentiation. Culture in hyperglycemic conditions disturbed the pancreatic lineage potential of hESC, leading to the downregulation of expression of pancreatic markers PDX1, NKX6-1 and NKX6-2 after in vitro differentiation. Genome-wide DNA methylome profiling revealed over 2000 differentially methylated CpG sites in hESC cultured in hyperglycemic condition when compared with those in control glucose condition. Gene ontology analysis also revealed that the hypermethylated genes were enriched in cell fate commitment. Among them, NKX6-2 was validated and its hypermethylation status was maintained upon differentiation into pancreatic progenitor cells. We also established mouse ESC lines at both physiological glucose level (PG-mESC) and conventional hyperglycemia glucose level (HG-mESC). Concordantly, DNA methylome analysis revealed the enrichment of hypermethylated genes related to cell differentiation in HG-mESC, including Nkx6-1. Our results suggested that hyperglycemia dysregulated the epigenome at early fetal development, possibly leading to impaired pancreatic development.

DNA Damage Response and Cell Cycle Regulation in Pluripotent Stem Cells.

Pluripotent stem cells (PSCs) hold great promise in cell-based therapy because of their pluripotent property and the ability to proliferate indefinitely. Embryonic stem cells (ESCs) derived from inner cell mass (ICM) possess unique cell cycle control with shortened G1 phase. In addition, ESCs have high expression of homologous recombination (HR)-related proteins, which repair double-strand breaks (DSBs) through HR or the non-homologous end joining (NHEJ) pathway. On the other hand, the generation of induced pluripotent stem cells (iPSCs) by forced expression of transcription factors (Oct4, Sox2, Klf4, c-Myc) is accompanied by oxidative stress and DNA damage. The DNA repair mechanism of DSBs is therefore critical in determining the genomic stability and efficiency of iPSCs generation. Maintaining genomic stability in PSCs plays a pivotal role in the proliferation and pluripotency of PSCs. In terms of therapeutic application, genomic stability is the key to reducing the risks of cancer development due to abnormal cell replication. Over the years, we and other groups have identified important regulators of DNA damage response in PSCs, including FOXM1, SIRT1 and PUMA. They function through transcription regulation of downstream targets (P53, CDK1) that are involved in cell cycle regulations. Here, we review the fundamental links between the PSC-specific HR process and DNA damage response, with a focus on the roles of FOXM1 and SIRT1 on maintaining genomic integrity.

Human embryonic stem cells as an in vitro model for studying developmental origins of type 2 diabetes.

The developmental origins of health and diseases (DOHaD) is a concept stating that adverse intrauterine environments contribute to the health risks of offspring. Since the theory emerged more than 30 years ago, many epidemiological and animal studies have confirmed that in utero exposure to environmental insults, including hyperglycemia and chemicals, increased the risk of developing noncommunicable diseases (NCDs). These NCDs include metabolic syndrome, type 2 diabetes, and complications such as diabetic cardiomyopathy. Studying the effects of different environmental insults on early embryo development would aid in understanding the underlying mechanisms by which these insults promote NCD development. Embryonic stem cells (ESCs) have also been utilized by researchers to study the DOHaD. ESCs have pluripotent characteristics and can be differentiated into almost every cell lineage; therefore, they are excellent in vitro models for studying early developmental events. More importantly, human ESCs (hESCs) are the best alternative to human embryos for research because of ethical concerns. In this review, we will discuss different maternal conditions associated with DOHaD, focusing on the complications of maternal diabetes. Next, we will review the differentiation protocols developed to generate different cell lineages from hESCs. Additionally, we will review how hESCs are utilized as a model for research into the DOHaD. The effects of environmental insults on hESC differentiation and the possible involvement of epigenetic regulation will be discussed.

Human embryonic stem cell-derived blastocyst-like spheroids resemble human trophectoderm during early implantation process.

OBJECTIVE: To study the use of human embryonic stem cell-derived trophoblastic spheroids (BAP-EB) as human blastocyst surrogates for studying early implantation and trophoblast development. DESIGN: Laboratory study. SETTING: University research laboratory. PATIENT(S): Infertile in vitro fertilization patients donating endometrial aspirates and human embryonic stem cells (hESCs: VAL3 and H9/WA09). INTERVENTION(S): In BAP-EB derived from hESC, transcriptomes analyzed by next-generation RNA sequencing, effects of Hippo signaling pathway studied by a YAP inhibitor, comparison of attachment of BAP-EB onto primary endometrial epithelial cells (EEC) collected at prereceptive and receptive phases, and antibody blocking assay used to study the molecule(s) involved in BAP-EB attachment. MAIN OUTCOME MEASURE(S): Gene expression profiles and endometrial cell attachment rates. RESULT(S): The BAP-EB differentiation protocol for VAL3 could be used to induce trophoblast differentiation in another hESC line, H9. Transcriptomic analysis showed that the epiblast signature gene expression was reduced while that of the trophoblast was induced during BAP-EB differentiation. Specifically, trophectoderm signature genes were induced in BAP-EB at 48 hours and 72 hours after induction of differentiation. The Hippo signaling pathway was one of the pathways induced during BAP-EB differentiation, and YAP1 inhibitor statistically significantly reduced attachment, outgrowth, and trophoblast gene expressions of BAP-EB. A statistically significantly higher number of BAP-EB derived from both VAL3 and H9 attached onto receptive EEC than prereceptive EEC. The antibody blocking assay demonstrated that endometrial E-cadherin might be critical in early implantation. CONCLUSION(S): The data suggest that BAP-EB possesses a trophectoderm-like signature, which supports the use of BAP-EB as a blastocyst surrogate for the study of trophoblast development and endometrial receptivity.

Sirt1 is regulated by miR-135a and involved in DNA damage repair during mouse cellular reprogramming.

Sirt1 facilitates the reprogramming of mouse somatic cells into induced pluripotent stem cells (iPSCs). It is regulated by micro-RNA and reported to be a target of miR-135a. However, their relationship and roles on cellular reprogramming remain unknown. In this study, we found negative correlations between miR-135a and Sirt1 during mouse embryonic stem cells differentiation and mouse embryonic fibroblasts reprogramming. We further found that the reprogramming efficiency was reduced by the overexpression of miR-135a precursor but induced by the miR-135a inhibitor. Co-immunoprecipitation followed by mass spectrometry identified 21 SIRT1 interacting proteins including KU70 and WRN, which were highly enriched for DNA damage repair. In accordance, Sirt1 activator resveratrol reduced DNA damage during the reprogramming process. Wrn was regulated by miR-135a and resveratrol partly rescued the impaired reprogramming efficiency induced by Wrn knockdown. This study showed Sirt1, being partly regulated by miR-135a, bound proteins involved in DNA damage repair and enhanced the iPSCs production.

Establishment of porcine and human expanded potential stem cells.

We recently derived mouse expanded potential stem cells (EPSCs) from individual blastomeres by inhibiting the critical molecular pathways that predispose their differentiation. EPSCs had enriched molecular signatures of blastomeres and possessed developmental potency for all embryonic and extra-embryonic cell lineages. Here, we report the derivation of porcine EPSCs, which express key pluripotency genes, are genetically stable, permit genome editing, differentiate to derivatives of the three germ layers in chimeras and produce primordial germ cell-like cells in vitro. Under similar conditions, human embryonic stem cells and induced pluripotent stem cells can be converted, or somatic cells directly reprogrammed, to EPSCs that display the molecular and functional attributes reminiscent of porcine EPSCs. Importantly, trophoblast stem-cell-like cells can be generated from both human and porcine EPSCs. Our pathway-inhibition paradigm thus opens an avenue for generating mammalian pluripotent stem cells, and EPSCs present a unique cellular platform for translational research in biotechnology and regenerative medicine.

Connexin 43 is involved in early differentiation of human embryonic stem cells.

Gap junctional intercellular communication (GJIC) is important for maintaining the pluripotency of mouse embryonic stem cells (mESC). However, human ESC (hESC) have a high level of connexin (Cx) molecules with unknown function. In this study, we found that the major Cx molecule, Cx43, was highly expressed in undifferentiated hESC. It was down-regulated upon spontaneously differentiation by embryoid body formation and induced differentiation along ectoderm, mesoderm and extraembryonic lineages, but up-regulated along endoderm differentiation. The knockdown of Cx43 and GJIC had no effect on the maintenance of hESC, as demonstrated by no morphological changes and similar expression levels of pluripotent markers (OCT4, NANOG, SSEA-3 and SSEA-4) and early differentiation markers (KRT8 and KRT18). Meanwhile, Cx43 knock down had no effect on endodermal markers (SOX17, FOXA2 and CXCR4) expression when hESC were differentiating into definitive endoderm lineage. On the contrary, it led to lower levels of mesodermal markers (CD56, CD34 and PDGFR-α) when cells were undergoing mesoderm differentiation. When compared to control, Cx43 knockdown led to higher attachment rate, HCG secretion and cell invasion of the hESC derived trophoblastic cells. Cx43 knockdown also resulted in up-regulated expressions of placental hormone (ß-hCG) and implantation related genes (LIFR, CDH5, LEP, PGF, TGFBR2). Our study suggested that Cx43 and GJIC had no effect on the undifferentiated growth of hESC but affected specific lineage differentiation.